The “thermoelectric effect” is the conversion of a thermal differential between opposing surfaces of a thermoelectric material to electric voltage, and vice versa. The thermoelectric effect, forms of which are known as the “Peltier effect” or the “Seebeck effect,” for one example, is the technology used in small electrical refrigeration systems used in portable beverage coolers and cars. Applying a voltage across a thermoelectric module causes a current to be driven through the semiconducting material of the thermoelectric module. The flow of current through the thermoelectric module causes the thermoelectric module to draw heat from a cooling side of the thermoelectric module to an opposing surface of the module. The cooling side is coupled with an enclosure that serves as a solid-state cooling device.
Conversely, the thermoelectric effect also can be used to generate electric voltage by disposing thermoelectric modules where one surface will be exposed to a relatively hot temperature, while an opposing surface will be exposed to a relatively cold temperature; instead of the voltage causing the thermal differential, the thermal differential is used to generate electric voltage.
FIG. 1 depicts a thermoelectric module 100 used to generate electric voltage. The thermoelectric module 100 is situated between a hot thermal source 110 and a cold thermal source 120, creating a thermal differential ΔH 130 between a first surface 140 of the thermoelectric module 100 presented to the hot thermal source 110 and a second surface 150 of the thermoelectric module 100 presented to the cold thermal source 120. As a result of the thermal differential 130, the thermoelectric module 100 generates a voltage differential ΔV 160.
Using thermoelectric modules to generate electrical power involves a number of concerns. First, the greater the thermal differential between the surfaces of the thermoelectric modules, the greater will be the voltage produced as a result of the thermoelectric effect. It is desirable, therefore, to dispose one side of the thermoelectric module to a much hotter or much colder environment than the opposing surface. If the thermal differential is too small, the thermoelectric modules will not generate enough voltage. Second, changes in the thermal differential affect the voltage generated. Thus, if the differential is less than anticipated, the thermoelectric module may not generate enough voltage. Alternatively, if the differential becomes greater than anticipated or desired, the thermoelectric module may produce too much voltage, and the excess voltage may damage devices that receive voltage from the thermoelectric module. Third, currently available thermoelectric modules are relatively fragile. Thus, in attempting to expose one surface of a thermoelectric module to a very hot environment in order to create a very high thermal differential, the high heat may damage the thermoelectric module.
There is growing interest in using thermoelectric modules to generate power. After all, countless engines, motors, furnaces, lights, electrical circuits, and other devices generate waste heat as a byproduct of their operation. Moreover, energy must be expended to cool these engines and other devices to keep them functioning or protect them from being damaged. Similarly, natural sources of heat, such as geothermal sources generate heat that represents a wasted opportunity for the generation of power. If this wasted or excess heat could be harnessed with thermoelectric modules, electrical energy could be generated from otherwise unused heat sources. Unfortunately, problems in maintaining sufficient thermal differentials, preventing excessive thermal differentials, or simply being unable to regulate thermal differentials undermines the practicality and effectiveness of using thermoelectric modules to generate electrical power.